Magnetic tape for reels, cassettes and the like must be manufactured within close tolerances, particularly with respect to width, skew and weave of the tape. The matter of tolerance is particularly critical in the case of video recording tape since the video recorders and playback machines are precision made and highly sensitive to any variations in tape width when utilized in the machines.
In the preparation of such tapes, the normal practice is to provide a relatively wide ribbon of tape and then slit this ribbon in a longitudinal direction, with spaced knives or equivalent cutting instruments.
With respect to the foregoing, one of the most successful types of tape slitters includes a frame supporting first and second arbors in spaced parallel relationship. The first arbor carries male cutting blades in the form of a plurality of discs in axially spaced positions while the second arbor carries female blades with engaging surfaces cooperating with the peripheries of the discs. The arrangement is such that a wide ribbon of tape passed between the arbors will be slit into parallel smaller width ribbons.
In some prior art systems, power has been provided to rotate the arbors and thereby feed the wide ribbon between the arbors and effect the cutting. In other improved prior art devices, air bearings or fine precision mechanical bearings have been so designed that no auxiliary power is required but rather simply pulling the wide ribbon of tape between the knives rotates the arbors to effect the slitting operation.
Over prolonged use of these devices, the cutting blades can become worn and as a result, it is necessary to either sharpen the same or in some instances simply to shift the first arbor axially with respect to the second arbor to increase the engagement force between the male and female blades, thereby compensating for such wear. In this particular operation, it is important to not exceed a given force which might warp the blades and thus result in improper cutting. On the other hand, enough force must be applied to assure that a cut will be made. In other words, there is an optimum force between the cutting blades for best results. For a given machine, this force can be determined empirically. Thereafter, a force gage is utilized in adjusting the force where such adjustment becomes necessary over extended periods of use.
Axial adjustments of one arbor with respect to the other is usually accomplished by guide rods and appropriate set screws and equivalent means for effecting the adjustment. Once an adjustment has been made and the proper force has been determined as by a gauge, the set screws are tightened to lock the assembly in place.
U.S. Pat. No. 3,899,948 is a good example of a typical prior art cutter, wherein an axial adjustment is provided. In this instance, individual lead screws in a frame portion are respectively adjusted and then a collar and bearing arrangement is locked to the arbor to maintain the adjusted position.
U.S. Pat. No. 3,994,193 shows another typical prior art slitter of the type under consideration wherein an axial loading is accomplished by an air bearing which may be supplemented by a spring if desired. In this case, the axial loading is adjusted by a needle valve which in turn adjusts the air pressure.